JPH09120564A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce cross talk from an adjacent track and to realize large capacity of a disk medium by increasing track density. SOLUTION: Two nearly circular first light spot 113 and second light spot 114 with different sizes are arranged separated in the track direction so that they aren't overlapped each other on a track central line 102 of the track that wobble pits 106 and 107 are formed on its both sides, and a timing pit 111 and a data pit 115 are formed on its just above. Then, the second light spot 114 is made be affected by the cross talk from the adjacent tracks (110, 112) more than another first light spot 113. Then, by operating a difference between signals of reflection light from respective first light spot 113 and second light spot 114 after performing level correction, timing correction, frequency characteristic correction, etc., a magneto-optical signal and a servo signal with less cross talk are regenerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc device for reproducing or recording and reproducing a signal by using a laser beam, and more particularly to a technique effectively applied to increase the storage capacity of a medium.

[0002]

2. Description of the Related Art For example, Nikkei BP, January 16, 1995, "Nikkei Electronics January 16 issue" P
As described in documents such as 67 to P78, the optical disc device reproduces or records and reproduces a signal along a track formed on the disc. The reproduction or recording / reproduction of a signal is performed by using one optical spot focused on the disc. That is, when the signal is reproduced, the information is read with the light intensity of the light spot that does not destroy the data pit, and when recording the signal, the light intensity of the light spot is increased to form the data pit and the signal is recorded. ing.

Regarding the optical disk device, a technique disclosed in, for example, Japanese Patent Laid-Open No. 6-295455 is known. That is, the sum of the elliptical information signal spots having a short axis in the track direction located in the center of the track and the two tracking spots having long axes in the track direction, which are respectively positioned at both side edges of the track. Information is reproduced and tracked by three light spots.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 6-267137, a main beam spot for recording information and a left and right sub-beam spots for tracking are respectively recorded on the groove portion and the land portions on both sides thereof. It is disclosed that the light is irradiated and the reflected light of the main beam spot and the left and right sub-beam spots is used to perform reproduction.

Further, in the technique disclosed in Japanese Patent Laid-Open No. 6-251396, the amplitude of a part of the light emitted from the light source is actively modulated, and a super-resolution spot having a small spot diameter and a beam are formed on the optical disk surface. A technique is disclosed in which a normal beam spot having a large diameter but capable of producing a high recording power is formed in a concentric shape, and servo control is performed using reflected light that is not modulated by the normal beam spot.

[0006]

In order to increase the amount of information recorded on an optical disk, it is necessary to improve the recording density in the track direction, that is, the so-called linear density, and also improve the track density. However, if the track density is reduced, that is, the track pitch is reduced, the amount of crosstalk, which is a phenomenon in which a signal recorded in an adjacent track leaks when a signal is reproduced, increases, and the error rate of the reproduced information increases. Will increase. For example, when the laser wavelength is 680 nm and the aperture lens has a numerical aperture of 0.55, the diameter of the light spot on the disk is about 1.2 μm. Therefore, when the track pitch is set to 1.0 μm or less, the end of the light spot comes into contact with the adjacent track, and the signal from that end leaks as crosstalk. Therefore, under the above conditions, the track pitch is 1.0 μm.
The degree was the limit.

In the techniques disclosed in Japanese Patent Laid-Open No. 6-295455 and Japanese Patent Laid-Open No. 6-267137, a plurality of light spots are arranged in the direction intersecting the tracks, which is disadvantageous in narrowing the track pitch. Is.

Further, the technique of the above-mentioned JP-A-6-251396 is advantageous for servo control, but does not consider reduction of crosstalk between tracks. Furthermore, in this conventional technique, since the super-resolution spot and the normal beam spot have the same wavelength generated from the same light source, it is impossible to independently control the light amounts of the two,
During recording, it is difficult to control the light amounts of the two light spots independently to perform various recording operations.

An object of the present invention is to provide an optical disk technology capable of increasing the track density and increasing the amount of data recorded / reproduced on / from a disk without concern about crosstalk from adjacent tracks.

Another object of the present invention is to provide an optical disc technology capable of performing various recording operations when recording information.

Still another object of the present invention is to provide an optical disc technology capable of performing various error verification operations at high speed during recording of information.

[0012]

In the optical disk device of the present invention, there are two first and second different shapes on the disk.
To form a light spot. One of the light spots is more than the other light spot and is arranged so as to detect crosstalk from the adjacent track. Further, by calculating the signals from each of these first and second light spots, a signal with less crosstalk is reproduced.

For example, crosstalk can be canceled by multiplying one of the signals read from the first and second light spots by a correction coefficient and then taking the difference between the two. When calculating the difference, when the positions of the first and second light spots are different in the track direction, it is possible to detect and correct the difference between the passing times of both light spots passing through the same position on the track. The time difference between the passing times can be corrected by measuring the time taken for the first and second light spots to pass through the reference mark provided on the track.

Further, for example, when the diameters of the first and second light spots in the track direction are different, frequency correction is performed together with an operation of multiplying one of the signals read from the first and second light spots by a correction coefficient. It can be applied to cancel crosstalk.

Further, for example, when information is recorded on the disc, one of the first and second light spots performs main recording, and the other light spot assists main recording. be able to. In this case, for example, one of the first and second light spots can perform main recording and the other light spot can perform preheating for main recording. Further, for example, one of the first and second light spots can be used for main recording, and the other light spot can be used for confirmation by reading out main recording. Further, for example, one of the first and second light spots can be used for main recording, and the other light spot can be used to confirm the writing state on the track before main recording is performed. Further, for example, one of the first and second light spots can be used for main recording, and the other light spot can be used for erasing a track before main recording is performed.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

In the following embodiments, a so-called magneto-optical disk for recording / reproducing information according to the direction of the perpendicularly magnetized film of the recording layer will be described as an example, but a phase for recording / reproducing information according to the crystalline state of the recording layer will be described. It may be a variable optical disk or a write-once optical disk that records and reproduces information by changing the shape of the recording layer. Further, regarding reproduction of the signal, a reproduction-only optical disk which only reproduces the signal may be used.

(Embodiment 1) A first embodiment of the present invention will be described. FIG. 1 is a conceptual diagram enlarging and exemplifying a part of the track on the disk in the first embodiment. Reference numerals 101, 102, and 103 are virtual track center lines indicating the centers of tracks for recording / reproducing information. The area on the track is divided into a servo area having pits for detecting a servo signal and generating a clock and a data area for recording / reproducing information.
Servo areas and data areas are provided alternately, but a part of them is shown in FIG. In the servo area, wobble pits 104 to 109 which are displaced from the track center line to the left and right of the track are provided. Further, timing pits 110 to 112 are provided on the track center line. This embodiment uses a so-called sample servo system. For example, when recording and reproducing data on the track 102, the wobble pits 106 and 107
Tracking is performed by applying a servo so that the amount of reflected light when the light spot passes in the vicinity of is the same. Further, a clock for recording / reproducing information is generated from the timing of passing through the timing pit 111. In the case of the first embodiment, two light spots are used, that is, a first light spot 113 having a substantially circular shape and a second light spot 114 having a substantially circular shape having a diameter larger than that of the first light spot 113. The second light spot covers the adjacent track more than the first light spot. By calculating the signal from the first light spot and the signal from the second light spot, the crosstalk from the adjacent track is reduced, which will be described later with reference to FIG. Data pits 115 are recorded on the tracks. In the present embodiment, the pits in the servo area are phase pits, and the data pits in the data area are so-called magneto-optical pits written according to the difference in the direction of perpendicular magnetization.

FIG. 24 is a diagram showing a conventional example. FIG.
The difference from the first embodiment illustrated in FIG. 3 is that recording / reproducing is performed only by the light spot 201. Assuming that the wavelength of the laser that forms the light spot 201 is λ and the numerical aperture of the lens is NA, the diameter D of the light spot 201 is approximately

[0020]

(Equation 1)

Is represented by On the other hand, the track pitch p is

[0022]

(Equation 2)

It was necessary to set Otherwise, the data pits of the adjacent tracks will hit the light spot 201, resulting in crosstalk and deterioration of the reproduced signal. By the way, if the wavelength λ is 680 nm and the lens numerical aperture NA is 0.55, the diameter D of the light spot 201 is
Was about 1.24 μm, and the track pitch p had to be about 1 μm or more. However, according to the first embodiment, crosstalk can be canceled even with a narrow track pitch that does not satisfy (Equation 2).

FIG. 2 shows an optical system according to the first embodiment. The optical disc 301 is rotated by a spindle motor (not shown). Laser diode 3
The light emitted from 02 is collimated by the collimator lens 303. The polarization direction of the light from the laser diode 302 is the direction within the plane of the drawing, and this is p-polarized light. The parallel light emitted from the collimator lens 303 passes through the diffraction element 304 and is divided into two parallel lights with slightly different traveling angles, but it is shown as one parallel light here. The light emitted from the beam splitter 305 is filtered by the focusing lens 306.
The optical disc 301 including the tracks is narrowed down. On the optical disc 301, the first light spot 113 of FIG.
And two light spots of the second light spot 114 are formed. The actuator 307 is the focusing lens 3
06 is moved to focus and track the light spot. The light reflected by the optical disc 301 is
Due to the Kerr effect of the medium, it has a polarization component in the direction perpendicular to the paper surface. This is s-polarized light, and its sign changes depending on whether or not information is recorded on the medium. The light reflected by the optical disk 301 is returned to the parallel light by the focusing lens 306 and guided to the beam splitter 305.
The light reflected by the beam splitter 305 is guided to the beam splitter 308. The light that has passed through the beam splitter 308 is narrowed down by the lens 309, split by the beam splitter 310, and then irradiated onto the detector 311 and the detector 312. Using the outputs of the detectors 311, 312, a defocus signal for focusing,
A track deviation signal for tracking is generated.
The light reflected by the beam splitter 308 is guided to the ½ wavelength plate 313.

The p-polarized component of the light incident on the half-wave plate 313 is Ep, and the s-polarized component is Es. The data signal component to be detected is Es. In the half-wave plate 313, the phase is rotated by 45 degrees, and the p-polarized component Ep ′ of the emitted light is

[0026]

(Equation 3)

And the s-polarized component Es' is

[0028]

(Equation 4)

## EQU1 ##

The light emitted from the half-wave plate 313 is the lens 3
It is narrowed down by 14 and guided to the polarization beam splitter 315. The Ep ′ component of the light goes straight through the polarization beam splitter 315 and is detected by the detector 316. The Es ′ component of the light is reflected by the polarization beam splitter 315 and detected by the detector 317. By taking the difference between Ep ′ and Es ′, the data signal component Es can be obtained, and by taking the sum of Ep ′ and Es ′, the reflected light amount component Ep can be obtained.
The coil 318 is for generating an external magnetic field for recording or erasing data pits.

FIG. 3 shows an example in which a diffraction grating is used as the diffraction element 304 in FIG. 2, and its details are shown. FIG. 3A shows a first example using a diffraction grating, and the diffraction grating 401 is viewed in the traveling direction of light.
A circular grating 402 is formed in the center of the diffraction grating 401, and its diameter is d. The lattice 402 is
It is located at the center of the light beam cross section 403. In reality, the grating 402 is engraved on the back side of the diffraction grating 401 with respect to the paper surface. FIG. 3B shows the diffraction grating 401 viewed from a direction perpendicular to the traveling direction of light. Regarding the light that has passed through the circular grating 402, the 0th-order light goes straight as shown by the solid line, but the traveling angle of the 1st-order diffracted light changes as shown by the dotted line. The luminous flux diameter of the first-order diffracted light is d, which is smaller than that of the zero-order light. When the primary light is focused on the disk, the effective numerical aperture is reduced, and the light spot has a large diameter. As described above, by narrowing the 0th-order light and the 1st-order light to the optical disk, the first light spot 113 and the second light spot 114 shown in FIG. 1 can be formed. Reference numeral 404 is an enlargement of the shape of the lattice 402 in FIG. Although the -1st-order diffracted light appears in the direction opposite to that of the 1st-order diffracted light shown by the dotted line in FIG. 3B, the -1st-order diffracted light is reduced by forming the grating into a sawtooth shape as indicated by 404. You can The diffraction angle of the first-order diffracted light and the intensity ratio of the 0th-order light and the 1st-order light can be controlled by the shape (pitch, height, etc.) of the grating 402. The intensity ratio of the 0th-order light and the 1st-order diffracted light, that is, the light amount ratio of the first light spot 113 and the second light spot 114 shown in FIG. 1 is set to 1: 1 in the case of an optical disk reproducing apparatus which only reproduces. However, in an optical disk recording / reproducing apparatus that also performs recording, it is normally 7
Set about 1 to 1. The reason is that the first light spot 113
This is to prevent the second light spot 114 from destroying the data pits when recording is performed.

FIG. 3C shows a second example in which a diffraction grating is used as the diffraction element 304, and the diffraction grating 405 is seen in the traveling direction of light. The diffraction grating 405 is engraved as a whole, and the grating is formed by cutting out a part of a concentric circle. The light beam cross section 406 is located at the center of the diffraction grating 405. In reality, the grating is assumed to be engraved on the back side of the plane of the diffraction grating 405. FIG. 3D shows the diffraction grating 405 viewed from a direction perpendicular to the traveling direction of light. In the light passing through the diffraction grating 405, the 0th-order light goes straight as shown by the solid line, while the 1st-order diffracted light changes its traveling angle as shown by the dotted line and becomes convergent light. When the primary light is focused on the disc, the focus position is different from that of the parallel 0th light,
When the focus control is performed by the 0th order light, the light spot has a large diameter due to defocus. In this way, by narrowing the 0th-order light and the 1st-order light to the optical disk 301, the first light spot 113 and the second light spot 114 shown in FIG.
Can be formed. Reference numeral 407 is an enlargement of the shape of the diffraction grating 405. Similar to FIG. 3B, the −1st-order diffracted light appears in the opposite direction to the 1st-order diffracted light shown by the dotted line in FIG. 3D, but as shown in 407, the grating shape should be sawtooth. Thus, the −1st order diffracted light can be reduced. The diffraction angle of the first-order diffracted light and the intensity ratio of the 0th-order light and the 1st-order light can be controlled by the shape of the grating (pitch, height, etc.).

FIG. 4 is an enlarged view of the detectors 316 and 317 of FIG. Two detectors are provided on each detector, and the reflected light of the first light spot and the second light spot focused on the disc are detected. The Ep ′ component of the reflected light of the first light spot 113 in FIG.
The Es ′ component is detected by the light receiving unit 503. FIG. 1
For the second light spot 114 of
The component is detected by the light receiving unit 502, and the Es ′ component is detected by the light receiving unit 504. The difference between the corresponding Ep 'and Es' components of the light spot gives the recorded magneto-optical signal, and the sum gives the reflected light amount signal. That is, the magneto-optical signal detected by the first light spot 113 in FIG.
The reflected light amount signal is the signal 506, the magneto-optical signal detected by the second light spot 114 in FIG. 1 is the signal 507, and the reflected light amount signal is the signal 508. These signals can be obtained as the outputs of the subtractor 509, the adder 510, the subtractor 511, and the adder 512, respectively.

FIG. 5 is a diagram for explaining an example of a method of reducing crosstalk from adjacent tracks in the first embodiment. 3 consecutive tracks 601, 6
02 and 603 have three data pits 60 of the same shape
4, 605 and 606 are arranged. The first light spot 113 and the second light spot 114 are the same as those shown in FIG. Here, the data pits 604, 6
Reference numerals 05 and 606 are separated in the track direction, and two data pits are not simultaneously applied to one light spot. The output of the magneto-optical signal detected from the reflected light when the two light spots pass on the track 602 is shown in the lower part of FIG. In the signal output Sm from the first light spot 113, the crosstalk from the data pit 604 of the adjacent track 601 is Smc, the signal output from the data pit 605 of the track 602 is Smm,
The crosstalk from the data pit 606 of the adjacent track 603 in the opposite direction is Smc. Second light spot 11
In the signal output Ss from No. 4, the crosstalk from the data pit 604 of the adjacent track 601 is Ssc, the signal output from the data pit 605 of the track 602 is Ssm, and the data pit 6 of the adjacent track 603 in the reverse direction is shown.
The crosstalk from 06 is Ssc. When crosstalk Smc and Ssc are compared, the second light spot 114
Is larger than the first light spot on the adjacent track, Ssc is larger than Smc.

In the signal output Sm, Smm is a target signal, and the crosstalk Smc is a harmful disturbance. Now, the ratio of Smc and Ssc is k, that is,

[0036]

(Equation 5)

It is assumed that The value obtained by subtracting k times the second signal output Ss from the first signal output Sm is defined as Sm '. That is,

[0038]

(Equation 6)

Then, the calculation output at the position where the data pit exists only in the adjacent track is Sm '(c) is

[0040]

(Equation 7)

Therefore, crosstalk can be canceled. The signal output Sm '(m) when there is only the target data pit is

[0042]

(Equation 8)

Is as follows.

In the above description, it is assumed that the same light spot does not reach two data pits. However, in the actual optical disc 301, the overlapping is established, so that a plurality of data pits 115 are simultaneously illuminated. Even if the spot is reached, the crosstalk can be reduced by performing the calculation of (Expression 6).

FIG. 6 is a block diagram showing an example of the overall configuration of the optical disk device according to the first embodiment. The optical system 701 is the one shown in FIG. Optical system 7
The output of the detector in 01 is the main reproduction signal detection circuit 70.
2 and the sub reproduction signal detection circuit 703. The main reproduction signal detection circuit 702 is composed of the subtractor 509 and the adder 5 shown in FIG.
10. The sub reproduction signal detection circuit 703 is composed of the subtractor 511 and the adder 512 shown in FIG. The reflected light amount signal 506 from the main reproduction signal detection circuit 702 is sent to the timing generation unit 704 and the phase shift detection circuit 705, and the magneto-optical signal 505 is sent to the arithmetic processing circuit 707. The reflected light amount signal 508 from the sub reproduction signal detection circuit 703 is sent to the phase shift detection circuit 705, and the magneto-optical signal 507 is
It is sent to the delay circuit 706. Timing generation unit 704
Is the timing pit 1 in the servo area shown in FIG.
A clock for recording and reproducing is generated from 10 to 112 and supplied to each unit. The phase shift detection circuit 705 measures the time difference between the two light spots from the time shift when the timing pits 110 to 112 are seen in the first light spot 113 and the second light spot 114, and the delay circuit 7
Output to 06. In the delay circuit 706, the magneto-optical signal 507
Is delayed and sent to the arithmetic processing circuit 707. Arithmetic processing circuit 7
In 07, the calculation as shown in the above (Equation 6) is performed on the two magneto-optical signals with the timing, and the crosstalk is canceled. The output of the arithmetic processing circuit 707 is equalized by the waveform equalization circuit 708, and further, the binarization circuit 70.
9 converts into a digital signal. Binarization circuit 709
Is sent to a higher-order control unit through the control unit 710. The control unit 710 is a unit that controls the entire apparatus. The laser driving unit 711 includes an optical system 701.
It is a portion for driving the laser diode 302 inside. The recording waveform generation unit 712 generates a waveform for driving the laser diode 302 when recording information on the optical disc 301.

FIG. 7 shows details of the arithmetic processing circuit 707 shown in FIG. The amplifier 801 can set the amplification factor according to an external command. This amplification factor corresponds to the value of k described above. The signal from the delay circuit 706 in FIG. 6 passes through the amplifier 801, and then is input to the frequency correction circuit 802. This is because when reproducing the data pit 115 with the first light spot 113 and the second light spot 114 in FIG. 1, there is a difference in the reproduction frequency characteristic of the data pit 115 between the two light spots, and this is corrected. It is a thing. The subtractor 803 takes the difference between the signal from the main reproduction signal detection circuit 702 and the output from the frequency correction circuit 802 in FIG. 6 and outputs it.

An example of a method for determining the amplification factor of the amplifier 801 shown in FIG. 7 will be described. Data pit 60 shown in FIG.
If test pits 4, 605 and 606 are provided on the optical disc 301, the amplification factor can be obtained by the procedure described in the description of FIG. A method of obtaining the amplification factor without providing the test pit will be described with reference to FIGS. 8 and 9.

When the crosstalk increases, the jitter of the reproduction signal increases, and the reproduction error increases. Therefore, the amplification factor of the amplifier 801 in FIG. 7 may be changed to evaluate the jitter of the reproduced signal, and the amplification factor that minimizes the jitter may be obtained. The circuit is shown in FIG. 8 and the difference from the circuit in FIG. 6 will be described. The amplification factor setting unit 901 sets the amplification factor of the arithmetic processing circuit 707 based on a command from the control unit 710. From the signal output of the waveform equalization circuit 708, the reproduction signal evaluation unit 902
Calculate the jitter of the reproduced signal. The memory 903 is
A pair of amplification factor and jitter is stored.

FIG. 9 shows an algorithm for determining the amplification factor that minimizes the jitter. The initial value of the amplification factor is set (step 1001). Next, the signal is reproduced and the jitter is measured (step 1002). The amplification factor value and the measured jitter value are written in the table in the memory 903 (step 1003). Next, the value of the amplification factor is increased (step 1004). It is judged whether or not the amplification factor has reached the final value (step 1005), and if it has not reached the final value, the process returns to the jitter measurement (step 1002). When the final value is reached, the amplification factor that minimizes the jitter is determined from the table of the amplification factor value and the measured data (step 10).
06). Since the value of the added amplification factor is discrete, the optimum amplification factor may be in the middle of the discrete values. Therefore, for example, the amplification factor that minimizes the jitter may be determined by performing the fitting by the least square method by the quadratic function approximation.

As described above, according to the first embodiment, a plurality of first light spots 113 and second light spots 114 having different shapes, that is, different crosstalk sensitivities from adjacent tracks are obtained. The crosstalk is canceled by appropriately correcting the received signal and then calculating the difference between the two, so even if the track density is increased and the crosstalk from the adjacent track becomes large, the crosstalk can be ensured. Can be reduced,
It is possible to increase the capacity of the optical disc 301 by increasing the track density.

(Second Embodiment) The second embodiment of the present invention will be described below. FIG. 10 shows the second embodiment of the present invention, and is an enlarged view of a part of the track on the optical disk. Portions different from the first embodiment shown in FIG. 1 will be described. The light spot has a roughly circular first
Light spot 1101 and an approximately elliptical second light spot 1102 having a short axis in the track direction. The second light spot 1102 is larger than the first light spot 1101 and covers the adjacent track. The second light spot 1
The minor axis length Ds of 102 is the first light spot 1101.
Is almost the same as the diameter Dm. Therefore, when the data pits are read by the first light spot 1101 and the second light spot 1102, the reproduction frequency characteristics of the two pits are almost the same. Therefore, the frequency correction circuit 802 shown in FIG. 7 is unnecessary, or the frequency correction amount is small, and problems such as increase in noise are less likely to occur.

FIG. 11 is a diagram showing an example of a diffraction grating for generating two light spots in the second embodiment. The diffraction grating 1201 shown here may be used as the diffraction element 304 in FIG. FIG.
(A) is a view of the diffraction grating 1201 in the traveling direction of light. The diffraction grating 1201 has a strip-shaped grating 1202.
Is carved and its height is h. Also, the lattice 120
2 is located at the center of the light beam cross section 1203. In reality, it is assumed that the grating 1202 is engraved on the back side of the diffraction grating 1201. FIG.
(B) is a view of the diffraction grating 1201 viewed from a direction perpendicular to the traveling direction of light. Regarding the light that has passed through the strip-shaped grating 1202, the 0th-order light goes straight as shown by the solid line, but the traveling angle of the 1st-order diffracted light changes as shown by the dotted line. Although the width of the first-order diffracted light remains almost the same, the height in the direction perpendicular to the paper surface is the height h of the strip-shaped grating. This primary light is the optical disk 30.
When the aperture is narrowed down to 1, the effective numerical aperture in the direction perpendicular to the paper surface decreases, so that an elliptical light spot having a major axis in this direction is formed. In this way, the 0th-order light and the 1st-order light are transmitted to the optical disc 3
By narrowing down to 01, the first light spot 1101 and the second light spot 1102 shown in FIG. 10 can be formed. Reference numeral 1204 denotes the lattice 1 of FIG.
The shape of 202 is enlarged. Although the -1st-order diffracted light appears in the direction opposite to that of the 1st-order diffracted light shown by the dotted line in FIG. 11B, the -1st-order diffracted light can be reduced by forming the grating into a sawtooth shape as indicated by 1204. You can The diffraction angle of the first-order diffracted light and the intensity ratio of the 0th-order light and the 1st-order light can be controlled by the shape (pitch, height, etc.) of the grating 1202. Normally, the intensity ratio of the 0th-order light and the 1st-order diffracted light, that is, the light quantity ratio of the first light spot 1101 and the second light spot 1102 shown in FIG. 10 is 1: 1 when only reproduction is performed. When recording also, it is about 7 to 1.
The reason is that, as in the case of the first embodiment, when recording with the first light spot 1101, the second light spot 11 is used.
This is because 02 does not destroy the data pit.

FIG. 12 is a diagram showing an example in which an acousto-optic element is used instead of the diffraction grating to generate the light spot of the second embodiment. The diffraction element 30 in FIG.
The acousto-optic element shown here may be used as 4.
FIG. 12A shows the acoustooptic device 1301 viewed in the traveling direction of light. The acousto-optic device 1301 has a light deflector 1302 at its center, and its height is h. The light deflector 1302 is separated from the other parts of the acousto-optic element 1301 and is located at the center with respect to the light beam cross section 1303. FIG. 12B shows a cross section of the light deflector 1302 of the acousto-optic device 1301 as seen from a direction perpendicular to the light traveling direction. Light deflector 130
At one end of 2, a thin film vibrator 13 made of, for example, a piezoelectric element
04 is attached. When the thin film oscillator 1304 is driven by the high frequency source 1305 and vibrated, a traveling wave traveling in the direction indicated by the arrow is generated in the optical deflector 1302. Although not shown in the figure, a vibration absorbing material may be attached to the opposite end of the thin film vibrator 1304 of the optical deflector 1302 so that the traveling wave is reflected and a standing wave is not generated. The light deflector 1302 is configured by using an acousto-optic material, and the traveling wave causes a dense / dense distribution of the acousto-optic material. Furthermore, the density distribution of this acousto-optic material becomes the distribution of the refractive index, and the light is deflected as a diffraction grating. That is, the light passing through the light deflector 1302 is 0
The secondary light travels straight as shown by the solid line, but the traveling angle of the primary diffracted light changes as shown by the dotted line. When the wavelength of the incident light is λ, the velocity of the traveling wave is v, the driving frequency of the high frequency source 1305 is f, and the diffraction angle of the light is θ,

[0054]

(Equation 9)

There is a relationship of

Since the wavelength λ of the incident light and the velocity v of the traveling wave are almost constant, the diffraction angle θ can be controlled by changing the driving frequency f. The behavior of the 0th-order light and the 1st-order diffracted light is the same as that described with reference to FIG. That is, the 0th-order light is focused on the disc as it is to form the first light spot 1101 shown in FIG. The width of the first-order diffracted light is almost the same as the original width, but the height in the direction perpendicular to the paper surface is the height h of the light deflector 1302. This primary light is the optical disc 3
When the aperture is narrowed to 01, the effective numerical aperture in the direction perpendicular to the paper surface decreases, so that an elliptical light spot having a major axis in this direction is formed, and the second light spot 1102 shown in FIG.
To form The diffraction angle θ of the 0th-order light and the 1st-order diffracted light can be controlled by the drive frequency f as described above, and thus the interval between the first light spot 1101 and the second light spot 1102 shown in FIG. Can be controlled. Further, in this example, by stopping the generation of the traveling wave in the thin film oscillator 1304, only the 0th order light can be obtained. That is, at the time of recording or erasing that requires laser power, only the 0th order light is used and the first light spot 1 in FIG.
Recording or erasing is performed at 101, and the 0th-order light and the 1st-order diffracted light are used at the time of reproduction to reproduce the first light spot 11
01 and the second light spot 1102 are formed to reduce crosstalk. Further, the intensity ratio of the 0th-order light and the 1st-order diffracted light can be controlled by the power when driving the thin film oscillator 1304 by the high frequency source 1305. In this example, since the 1st-order diffracted light can be generated only during reproduction, the intensity ratio of the 0th-order light and the 1st-order diffracted light, that is, the light amounts of the first light spot 1101 and the second light spot 1102 shown in FIG. The ratio can be set arbitrarily. Normally, the S / N ratio during playback (the ratio of signal to noise)
Is set to be the maximum.

FIG. 13 shows details of the high frequency source 1305 shown in FIG. The high frequency oscillation circuit 1401 generates a high frequency that is a source for driving the acousto-optic element 1404. The switch 1402 switches whether or not to transmit the signal from the high-frequency oscillation circuit 1401 to the variable amplifier 1403 at the subsequent stage, based on a command from the host controller. With the switch 1402, switching is performed between only the 0th-order light and the 0th-order light and the 1st-order diffracted light as described above.
The variable amplifier 1403 can change the amplification factor based on a command from the host. 0 by changing the amplification factor
It is possible to control the intensity ratio of the second-order light and the first-order diffracted light, that is, the light amount ratio between the first light spot 1101 and the second light spot 1102 shown in FIG.

As described above, according to the second embodiment, it is possible to obtain the same effect as that of the above-described first embodiment and to eliminate the need for the frequency correction circuit and the like.
Alternatively, it is possible to obtain an effect that a correction amount is small and a problem such as an increase in noise can be avoided.

(Third Embodiment) The third embodiment of the present invention will be described below. FIG. 14 shows the third embodiment of the present invention, and is an enlarged view of a part of the track on the optical disk. Reference numerals 1501, 1502, and 1503 denote track centerlines indicating the centers of tracks for recording / reproducing information. Grooves 1504 to 1 between tracks
507 is engraved. In the present embodiment, since the tracking signal is generated using the diffracted light from the groove, the wobble pit as in the first and second embodiments is unnecessary. Data pits 1508 are recorded on the tracks. In the present embodiment, it is assumed that the data pits are so-called magneto-optical pits written by the difference in the direction of perpendicular magnetization. The light spots are a substantially circular first light spot 1509 by the laser light of the first wavelength and a second substantially circular light spot 1510 having a diameter larger than that of the first light spot 1509 by the laser light of the second wavelength. There is. The second light spot 1510 is larger than the first light spot 1509 on the adjacent track. Also, the first light spot 150
9 and the center of the second light spot 1510 are supposed to coincide with each other. Since the centers of the first light spot 1509 and the second light spot 1510 coincide with each other, the timings of reading information from the two light spots coincide with each other. Therefore, the timing pit as in the first and second embodiments is unnecessary. The clock for reproducing information is generated from the data pit. The signal from the first light spot 1509 and the second light spot 151
By calculating the signal from 0, the crosstalk from the adjacent track is reduced, but this is based on the same principle as in the first and second embodiments described above.

FIG. 15 shows an optical system according to the third embodiment. The optical disc 1601 is rotated by a spindle motor (not shown). The light emitted from the laser diode 1602 having the first wavelength is collimated by the collimator lens 1603. The polarization direction of the light from the laser diode 1602 of the first wavelength is in the plane of the paper,
This is p-polarized light. Collimating lens 16
The parallel light exiting from 03 enters the wavelength synthesizing prism 1604 and goes straight through this. On the other hand, the light emitted from the laser diode 1605 of the second wavelength is collimated by the collimator lens 1606.
It becomes parallel light. Second wavelength laser diode 160
The polarization direction of the light from 5 is also in the plane of the paper, and this is p-polarized light. The parallel light emitted from the collimator lens 1606 enters the wavelength combining prism 1604 and is reflected here. The first and the second emitted from the wavelength combining prism 1604
It is assumed that the laser beams of the wavelengths have the same optical axis and the same emitting direction. The light emitted from the wavelength combining prism 1604 is
Go straight through the beam splitter 1607. The light emitted from the beam splitter 1607 is narrowed down by the narrowing lens 1608 to the optical disc 1601 including the track. On the optical disc 1601, a first light spot 1509 by the laser light of the first wavelength and a second light spot 1510 by the laser light of the second wavelength of FIG. 14 are formed. If the first wavelength is shorter than the second wavelength,
First light spot 1509 by laser light of first wavelength
Is the second light spot 15 due to the laser light of the second wavelength.
It will be less than 10. Actuator 1609
Moves the stop lens 1608 to perform focusing and tracking of the light spot. The light reflected by the optical disc 1601 has a polarization component in the direction perpendicular to the paper surface due to the Kerr effect of the medium. This is s-polarized light, and its sign changes depending on whether or not information is recorded on the medium. The light reflected by the optical disc 1601 is
The collimated light is again returned by the focusing lens 1608 and is guided to the beam splitter 1607. Beam splitter 1
The light reflected by 607 is guided to the wavelength separation prism 1610. In the wavelength separation prism 1610, light of one wavelength goes straight and light of another wavelength is reflected.
Here, it is assumed that the light of the first wavelength goes straight and the light of the second wavelength is reflected, but the reverse is also possible. The light of the first wavelength that has proceeded straight through the wavelength separation prism 1610 enters the beam splitter 1611. Beam splitter 161
The light of the first wavelength that has passed through 1 is narrowed down by the lens 1612 and split by the beam splitter 1613.
The detector 1614 and the detector 1615 are irradiated. Outputs of the detectors 1614 and 1615 are used to generate a focus shift signal for focusing and a track shift signal for tracking. The light of the first wavelength reflected by the beam splitter 1611 is guided to the ½ wavelength plate 1616. The p-polarized component of the light of the first wavelength incident on the half-wave plate 1616 is Ep, and the s-polarized component is E.
s. The data signal component to be detected is Es. 1
In the / 2 wave plate 1616, the phase is rotated by 45 degrees, the p-polarized light component Ep 'of the emitted light becomes the value shown in (Formula 3), and the s-polarized component Es' is the value shown in (Formula 4). Becomes

The light of the first wavelength emitted from the half-wave plate 1616 is focused by the lens 1617 and guided to the polarization beam splitter 1618. The Ep 'component of the light of the first wavelength is
Go straight through the polarization beam splitter 1618, and the detector 1
619. The Es' component of the light of the first wavelength is
It is reflected by the polarization beam splitter 1618 and is detected by the detector 16
Detected at 20. By taking the difference between Ep ′ and Es ′, the data signal component Es can be obtained, and by taking the sum of Ep ′ and Es ′, the reflected light amount component Ep can be obtained. The light of the second wavelength reflected by the wavelength separation prism 1610 is
It is guided to the half-wave plate 1621. The principle of signal detection is the same as in the case of the light of the first wavelength, and will be omitted. The light of the second wavelength emitted from the half-wave plate 1621 is reflected by the lens 1622.
It is focused by and is guided to the polarization beam splitter 1623.
The Ep ′ component of the light of the second wavelength goes straight through the polarization beam splitter 1623 and is detected by the detector 1624.
The Es ′ component of the light of the second wavelength is reflected by the polarization beam splitter 1623 and detected by the detector 1625. The coil 1626 is for generating an external magnetic field for recording or erasing the data pit 1508.

FIG. 16 shows detectors 1619 and 1620 for detecting signals from the light of the first wavelength shown in FIG.
The detectors 1624 and 1625 for detecting the signals from the light of the wavelength are expanded. There is a light receiving portion on each detector, and the first light focused on the optical disk 1601
The reflected light of the first light spot 1509 due to the light of the wavelength and the reflected light of the second light spot 1610 due to the light of the second wavelength are detected. The Ep ′ component of the reflected light of the first light spot 1509 due to the light of the first wavelength in FIG.
The s ′ component is detected by the light receiving unit 1702. Similarly, FIG.
For the second light spot 1510 of the second wavelength of light, the Ep ′ component of the reflected light is the light receiving portions 1703, Es ′.
The component is detected by the light receiving unit 1704. The difference between the corresponding Ep 'and Es' components of the light spot gives the recorded magneto-optical signal, and the sum gives the reflected light amount signal. That is, the magneto-optical signal detected by the first light spot 1509 by the light of the first wavelength in FIG. 14 is the signal 1705,
The reflected light amount signal is the signal 1706, and the magneto-optical signal detected by the second light spot 1510 by the light of the second wavelength in FIG. 14 is the signal 1707. These signals are output to the subtractor 1708, the adder 1709, and the subtractor 171 respectively.
It can be obtained as an output of 0.

The method of reducing the crosstalk from the adjacent tracks in the third embodiment is the same as the principle described in the first embodiment with reference to FIG.

FIG. 17 is a block diagram showing an example of the overall configuration of the optical disk device according to the third embodiment. The optical system 1801 is the one shown in FIG. Optical system 18
The output of the detector in 01 is the main reproduction signal detection circuit 18
02 and the sub reproduction signal detection circuit 1803. The main reproduction signal detection circuit 1802 is a subtractor 1708 shown in FIG.
The adder 1709 and the sub reproduction signal detection circuit 1803 are shown in FIG.
The subtractor 1710 shown in FIG. The reflected light amount signal 1706 from the main reproduction signal detection circuit 1802 is sent to the timing generation unit 1804, and the magneto-optical signal 1705 is transmitted.
Is the timing generation unit 1804 and the arithmetic processing circuit 18.
05. The magneto-optical signal 1707 from the sub reproduction signal detection circuit 1803 is sent to the arithmetic processing circuit 1805.

In the diagram showing the entire block in the above-mentioned first embodiment shown in FIG.
The magneto-optical signal 507 from the signal 03 is sent to the delay circuit 706 after the timing is adjusted by the delay circuit 706. The magneto-optical signal 1707 from the sub reproduction signal detection circuit 1803 is sent to the arithmetic processing circuit 1805 as it is without the need for matching. The timing generation unit 1804 generates a clock for reproduction from the recorded data pits 1508 at the time of reproduction, generates a clock for recording from the reference clock inside the timing generation unit 1804 at the time of recording, and supplies it to each unit. The arithmetic processing circuit 1805 cancels the crosstalk by performing the arithmetic operation as described in (Equation 6) on the two magneto-optical signals. The output of the arithmetic processing circuit 1805 is equalized by the waveform equalization circuit 1806, and further 2
The digitization circuit 1807 converts the digital signal. 2
The output of the digitization circuit 1807 is sent to the higher-order control unit through the control unit 1808. The control unit 1808 is a unit that controls the entire apparatus. Laser drive unit 1
Reference numeral 809 denotes a portion that drives two laser diodes in the optical system 1801. The recording waveform generation unit 1810 generates a waveform for driving the two laser diodes 1602 and 1605 when recording information on the optical disc 1601. For details of the arithmetic processing circuit 1805,
It is similar to that shown in FIG.

In the third embodiment, since the two light spots are formed by the light from the separate laser diodes 1602 and 1605, the light quantity of each light spot can be individually controlled. Therefore, when recording or erasing,
When the output of the laser diode is insufficient, two light spots can compensate each other. An example thereof will be described with reference to FIG.

FIG. 18A shows a first light spot 1509 formed by laser light of a first wavelength on the track 1502.
And the first light spot 15 by the laser light of the second wavelength.
FIG. 18B is a diagram in which the second light spot 1510 having a diameter larger than 09 is scanning, and FIGS. 18B to 18D show the light amount of the light spot corresponding to the position in the track direction. Hereinafter, the light amount of the first light spot 1509 is Pm and the light amount of the second light spot 1510 is Ps. FIG. 18B shows the light quantity Pm of the first light spot 1509 and the light quantity Ps of the second light spot 1510 during reproduction. Pm and Ps are set so as not to destroy recorded data pits and maximize the S / N ratio (ratio of signal to noise) of the reproduced signal. FIG.
(C) is the light amount P of the first light spot 1509 during recording.
m or the light amount Ps of the second light spot 1510 is shown. When recording is performed using the first light spot 1509, since it is smaller than the second light spot 1510, minute pits can be written, which is suitable for increasing the data density. However, the first light spot 150
The wavelength of the laser forming 9 is the second light spot 151.
In some cases, the light quantity Pm cannot be made large because the wavelength is shorter than the wavelength of the laser that forms 0. In that case, the second light spot 15
Recording can also be performed using 10. Furthermore, FIG.
As shown in (d), the light amount can be complemented by the light amount Pm of the first light spot 1509 and the light amount Ps of the second light spot 1510. FIG. 18D is the same as FIG.
This is an example in which the recording waveform of (c) is complemented by the light quantity Pm of the first light spot 1509 and the light quantity Ps of the second light spot 1510. Since the pits are formed in the comb-shaped pulse portion shown in the upper diagram of FIG. 18D, FIG.
The light intensity P of the first light spot 1509
In m, it is preferable to share the waveform in the lower diagram of FIG. 18D with the light amount Ps of the second light spot 1510.

As described above, according to the third embodiment, the same effect as that of the above-described first embodiment can be obtained, and further, the two wavelengths which are concentrically irradiated on the optical disk 1601 are obtained. Two different first light spots 15
09 and the second light spot 1510 eliminates the need for timing control for canceling crosstalk during reproduction, and can increase the recording density by omitting the timing pits on the medium. By individually controlling the light quantities of the light spot 1509 and the second light spot 1510, it is possible to obtain the effect that various recording operations can be realized.

(Fourth Embodiment) The fourth embodiment of the present invention will be described below. FIG. 19 shows the fourth embodiment of the present invention, and is an enlarged view of a part of the track on the optical disc. The difference from the first embodiment shown in FIG. 1 is that the wavelengths of the first light spot 2001 and the second light spot 2002 are different, and therefore the respective light amounts can be set independently.

FIG. 20 shows an optical system according to the fourth embodiment. First wavelength laser diode 2
The light emitted from 101 is collimated by the collimator lens 2102. The polarization direction of the light from the laser diode 2101 having the first wavelength is the direction within the plane of the drawing, and this is p-polarized light. The parallel light emitted from the collimator lens 2102 enters the wavelength synthesizing prism 2103, and goes straight on. On the other hand, the light emitted from the laser diode 2104 having the second wavelength is collimated by the collimator lens 2105.
The polarization direction of the light from the laser diode 2104 having the second wavelength is also in the plane of the paper, and this is p-polarized light. The parallel light emitted from the collimator lens 2105 enters the wavelength combining prism 2103 and is reflected here. The laser beams of the first and second wavelengths emitted from the wavelength synthesizing prism 2103 pass through the deflection prism 2106 and are divided into two parallel lights having slightly different traveling angles, but shown as one parallel light here. The other parts of the optical system are similar to those of the first embodiment shown in FIG.

FIG. 21 shows the deflection prism 2 shown in FIG.
The details of 106 are shown. Deflection prism 2106
Is a combination of two triangular prisms 2201 and 2202. The triangular prisms 2201 and 2202 have the same refractive index for the first wavelength and different refractive indexes for the second wavelength. Therefore, FIG.
As shown in, the laser light of the first wavelength travels straight, and the emitted light of the laser light of the second wavelength is deflected.

Detector, principle of crosstalk reduction,
The configuration of the whole block and the like are the same as those in the first embodiment, and will be omitted. In the fourth embodiment, two light spots are formed by light from separate laser diodes 2101 and 2104 as in the third embodiment described above.
The light quantity of each light spot can be controlled individually. Therefore, various operations can be performed with the two light spots. An example thereof will be described with reference to FIGS.

FIG. 22A shows a first light spot 2001 by laser light of a first wavelength on a track 2301.
And the first light spot 20 by the laser light of the second wavelength.
It is a figure which the 2nd light spot 2002 with a diameter larger than 01 is scanning, and Drawing 22 (b) -Drawing 22 (f) show the light quantity of the light spot corresponding to the position of the track direction. Hereinafter, the light amount of the first light spot 2001 is Pm, and the light amount of the second light spot 2002 is Ps.

FIG. 22B shows the light quantity Pm of the first light spot 2001 and the light quantity Ps of the second light spot 2002 during reproduction. The light amounts Pm and Ps are
It is set so as not to destroy the recorded data pits and to maximize the S / N ratio (ratio of signal to noise) of the reproduced signal. Light intensity Pm and Ps at that time
Are Prm and Prs, respectively.

FIG. 22C shows the light amount Pm of the first light spot 2001 or the second light spot 2002 during recording.
The amount of light Ps is shown. As in the case of FIG. 18C of the third embodiment described above, if recording is performed using the first light spot 2001, a minute pit can be written because it is smaller than the second light spot 2002, It is suitable for increasing the data density. However, the wavelength of the laser that forms the first light spot 2001 is shorter than the wavelength of the laser that forms the second light spot 2002, and the light amount Pm may not be large. In that case, recording can also be performed using the second light spot 2002.

FIG. 22D is an example in which the recording waveform of FIG. 22C is complemented by the light quantity Pm of the first light spot 2001 and the light quantity Ps of the second light spot 2002. The waveform in the upper diagram of FIG. 22D has the first light spot 200.
The light amount Pm of 1 is the second waveform in the lower diagram of FIG.
The light amount Ps of the light spot 2002 is shown. Preceding second
Optical disc 1601 with the light amount Ps of the light spot 2002 of
Of the first light spot 2001 following
A pit is formed in the portion of the comb-shaped pulse having the light amount Pm of. Since the first light spot 2001 passes through a certain position of the optical disc 1601 a while after the second light spot 2002 passes, the second light spot 2002 passes two at the same time.
18D of the above embodiment, the light quantity Ps of the second light spot 2002 is set higher.

In FIG. 22E, the waveform in the upper diagram shows the light amount Pm of the first light spot 2001, and the waveform in the lower diagram shows the light amount Ps of the second light spot 2002. The amount of light Pm is set to the reproduction power Prm, and recording is performed with the preceding second light spot 2002 and reproduction is performed with the following first light spot 2001 to confirm whether or not the recording is normally performed. is there.

Also in FIG. 22F, the waveform in the upper diagram shows the light amount Pm of the first light spot 2001, and the waveform in the lower diagram shows the light amount Ps of the second light spot 2002. The light amount Ps is set to the erasing power Pe, and information is erased by the preceding second light spot 2002 while recording is performed by the following first light spot 2001.

FIG. 23A shows a first light spot 2001 on the track 2401 by the laser light of the first wavelength.
And the first light spot 20 by the laser light of the second wavelength.
It is a figure which the 2nd light spot 2002 with a diameter larger than 01 is scanning, and Drawing 23 (b) -Drawing 23 (f) show the light quantity of the light spot corresponding to the position of the track direction. Hereinafter, the light amount of the first light spot 2001 is Pm, and the light amount of the second light spot 2002 is Ps. FIG. 22A shows a first light spot 2001 and a second light spot 20.
The position of 02 is reversed, which means that the deflecting prism 2106 is placed on the opposite side in FIG.
1 can be realized by setting the refractive indexes of the triangular prisms 2201 and 2202.

FIG. 23B shows the light quantity Pm of the first light spot 2001 and the light quantity Ps of the second light spot 2002 during reproduction. Similar to FIG. 22 (b),
The light amounts Pm and Ps are set so as not to destroy recorded data pits and maximize the S / N ratio (ratio of signal to noise) of the reproduced signal. The light amounts Pm and Ps at that time are respectively Prm and Prs.
And

FIG. 23C shows the light amount Pm of the first light spot 2001 or the second light spot 2002 during recording.
The amount of light Ps is shown. Similar to FIG. 22 (c),
If recording is performed using the first light spot 2001, the second
Since it is smaller than the light spot 2002, a minute pit can be written, which is suitable for increasing the data density. However, the wavelength of the laser that forms the first light spot 2001 is shorter than the wavelength of the laser that forms the second light spot 2002, and the light amount Pm may not be large. In that case, recording can also be performed using the second light spot 2002.

FIG. 23D shows an example in which the recording waveform of FIG. 23C is complemented by the light quantity Pm of the first light spot 2001 and the light quantity Ps of the second light spot 2002. The waveform in the upper diagram of FIG. 23D is the first light spot 200.
The light amount Pm of 1 is the second waveform in the lower diagram of FIG.
The light amount Ps of the light spot 2002 is shown. Preceding first
The disk is preheated with the light amount Pm of the second light spot 2001, and the light amount Ps of the subsequent second light spot 2002 is
A pit is formed in the portion of the comb-shaped pulse. The second light spot 2002 passes a certain position after the first light spot 2001 passes through a certain position of the disc, so that the two light spots pass at the same time as shown in FIG.
The light quantity Pm of the first light spot 2001 is set higher than that in (d).

In FIG. 23E, the waveform in the upper diagram shows the light amount Pm of the first light spot 2001, and the waveform in the lower diagram shows the light amount Ps of the second light spot 2002. The light amount Pm is set to the reproduction power Prm, reproduction is performed with the preceding first light spot 2001, and pre-recording check is performed to determine whether there is an unerased residue or a disc defect. Recording is performed at the spot 2002.

Also in FIG. 23F, the waveform in the upper figure shows the light quantity Pm of the first light spot 2001, and the waveform in the lower figure shows the light quantity Ps of the second light spot 2002. The amount of light Ps is set to the reproduction power Prs, and recording is performed with the preceding first light spot 2001, while reproduction is performed with the following second light spot 2002, and it is confirmed whether recording has been performed normally. Is.

In the case of the fourth embodiment, as described above, the two first light spots 2001 and the second light spots 2001 and the second light spots which are arranged at different positions on the same track center line 2301 (2401) in the track direction. By using the light spot 2002, recording is performed with the preceding first light spot 2001 (second light spot 2002) and reproduction is performed with the following second light spot 2002 (first light spot 2001). Since the confirmation operation (read-after-write) at the time of recording information is performed, the read-after-write can be performed without waiting for rotation, and the reliability of the recording operation can be secured and the speed of the recording operation can be increased.

As described above, according to the fourth embodiment, the two first light spots 2001 and the second light spots 20 having different wavelengths whose light amounts can be controlled independently of each other.
By arranging 02 at different positions in the track direction on the same track center line, the same effect as that of the first embodiment can be obtained, and at the time of recording, various operations can be performed at high speed without waiting for rotation. The effect that the error verification operation can be performed is obtained.

Although the invention made by the present inventor has been specifically described based on the embodiments, the invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say.

For example, the shapes of the individual light spots are not limited to those exemplified in the above-mentioned respective embodiments, but can be variously changed.

[0089]

According to the optical disk device of the present invention, it is possible to increase the track density and increase the amount of data recorded / reproduced on / from the disk without concern about crosstalk from adjacent tracks. To be

According to the optical disk device of the present invention,
The effect that various recording operations can be performed when recording information is obtained.

According to the optical disk device of the present invention,
The effect that various error verification operations at the time of recording information can be performed at high speed is obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram enlarging and illustrating a part of a track on an optical disc in an optical disc device according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing an example of an optical system in the optical disc device according to the first embodiment of the present invention.

FIG. 3 is a conceptual diagram showing an example of a diffractive element that constitutes an optical system in the optical disc device according to the first embodiment of the present invention.

FIG. 4 is a conceptual diagram showing an example of a detector that constitutes an optical system in the optical disc device according to the first embodiment of the present invention.

FIG. 5 is a conceptual diagram showing an example of a principle of crosstalk reduction in the optical disc device according to the first embodiment of the present invention.

FIG. 6 is a block diagram showing an example of the overall configuration of the optical disc device according to the first embodiment of the present invention.

FIG. 7 is a block diagram showing an example of an arithmetic processing circuit of the optical disc device according to the first embodiment of the present invention.

FIG. 8 is a block diagram showing a modified example of determination of an amplification factor in the optical disc device according to the first embodiment of the present invention.

FIG. 9 is a flowchart showing an example of an algorithm of a modified example of determining the amplification factor in the optical disc device according to the first embodiment of the present invention.

FIG. 10 is a conceptual diagram enlarging and illustrating a part of a track on an optical disc in an optical disc device according to a second embodiment of the present invention.

FIG. 11 is a conceptual diagram showing an example of a diffractive element that constitutes an optical system in an optical disc device according to a second embodiment of the present invention.

FIG. 12 is a conceptual diagram showing an example of a diffractive element that constitutes an optical system in an optical disc device according to a second embodiment of the present invention.

FIG. 13 is a block diagram showing an example of details of a high-frequency source forming an optical system in the optical disc device according to the second embodiment of the present invention.

FIG. 14 is a conceptual diagram enlarging and illustrating a part of a track on an optical disc in an optical disc device according to a third embodiment of the present invention.

FIG. 15 is a conceptual diagram showing an example of an optical system in an optical disc device according to a third embodiment of the present invention.

FIG. 16 is a conceptual diagram showing an example of a detector that constitutes an optical system in an optical disc device that is a third embodiment of the present invention.

FIG. 17 is a block diagram showing an example of the overall configuration of an optical disc device according to a third embodiment of the present invention.

FIG. 18 is a conceptual diagram showing an example of an operation of a light spot in the optical disc device according to the third embodiment of the present invention.

FIG. 19 is a conceptual diagram enlarging and illustrating a part of a track on a disc in an optical disc device according to a fourth embodiment of the present invention.

FIG. 20 is a conceptual diagram showing an example of an optical system in an optical disc device according to a fourth embodiment of the present invention.

FIG. 21 is a conceptual diagram showing an example of a diffractive element that constitutes an optical system in an optical disc device according to a fourth embodiment of the present invention.

FIG. 22 is a conceptual diagram showing an example of the operation of a light spot in the optical disc device according to the fourth embodiment of the present invention.

FIG. 23 is a conceptual diagram showing an example of the operation of a light spot in the optical disc device according to the fourth embodiment of the present invention.

FIG. 24 is a conceptual diagram enlarging and illustrating a part of a track on an optical disc in a conventional optical disc device.

[Explanation of symbols]

113 ... First light spot, 114 ... Second light spot, 301 ... Optical disk, 302 ... Laser diode,
303 ... Collimating lens, 304 ... Diffractive element, 306
... Focusing lens, 316 ... Detector, 317 ... Detector, 401 ... Diffraction grating, 405 ... Diffraction grating, 701
Optical system 702 Main reproduction signal detection circuit 703 Sub reproduction signal detection circuit 704 Timing generator 705
Phase shift detection circuit, 706 ... Delay circuit, 707 ... Arithmetic processing circuit, 708 ... Waveform equalization circuit, 709 ... Binarization circuit,
710 ... Control unit, 711 ... Laser drive unit, 712 ... Recording waveform generation unit, 801 ... Amplifier, 802 ... Frequency characteristic correction circuit, 901 ... Amplification factor setting unit, 902 ... Reproduction signal evaluation unit, 903 ... Memory, 1101 ... 1 light spot, 1
102 ... second light spot, 1201 ... diffraction grating, 13
01 ... Acousto-optic element, 1302 ... Optical deflector, 1401 ...
High-frequency oscillator circuit, 1509 ... First light spot, 151
0 ... second light spot, 1601 ... optical disk, 160
2 ... Laser diode, 1603 ... Collimating lens,
1605 ... Laser diode, 1606 ... Collimating lens, 1608 ... Focusing lens, 1619 ... Detector, 1620 ... Detector, 1624 ... Detector, 1
625 ... Detector, 1801 ... Optical system, 1802 ... Main reproduction signal detection circuit, 1803 ... Sub reproduction signal detection circuit, 1
804 ... Timing generation unit, 1805 ... Arithmetic processing circuit,
1806 ... Waveform equalization circuit, 1807 ... Binarization circuit, 18
08 ... control unit, 1809 ... laser drive unit, 1810 ... recording waveform generation unit, 2001 ... first light spot, 2002
... second light spot, 2101 ... laser diode, 2
102 ... Collimating lens, 2104 ... Laser diode, 2105 ... Collimating lens, 2106 ... Deflection prism.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichiro Wakabayashi 1-280, Higashi Koigakubo, Kokubunji, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. (72) Inventor Hidehiko Kondo 2880, Kozu, Odawara-shi, Kanagawa Hitachi Storage Co., Ltd. System Division (72) Inventor Yasuhiko Souyoshi 2880 Kozu, Odawara City, Kanagawa Stock Company Hitachi Storage Systems Division

Claims (6)

[Claims] 1. An optical disk device for recording and / or reproducing a signal along a track formed on a disk, wherein the first light spot and the first light spot have a size and a shape. A second light spot different in at least one of the first light spot and an optical system for narrowing the second light spot onto the disc, and the first light read from the first light spot.
Signal and at least one of the second signal read from the second light spot, and then at least one of information reproduction and tracking control by calculating the difference between the first and second signals. An optical disk device for performing the following. 2. The optical disk device according to claim 1, wherein the first and second light spots are formed by laser lights of the same wavelength and are substantially circular light spots having different diameters from each other. An optical disk device, wherein the centers of the second light spots are located at different positions on the same track. 3. The optical disk device according to claim 1, wherein the first and second light spots are formed by laser light of the same wavelength, and have substantially circular diameters in the track direction, and Consisting of a substantially elliptical light spot having a minor axis in the track direction,
An optical disk device, wherein the centers of the first and second light spots are located at different positions on the same track. 4. The optical disk device according to claim 1, wherein the first and second light spots are formed by laser beams having different wavelengths, and are substantially circular light spots having different diameters. An optical disk device, wherein the second light spots are concentrically positioned on the same track. 5. The optical disc device according to claim 1, wherein the first and second light spots are formed by laser beams having different wavelengths, and are substantially circular light spots having different diameters. An optical disk device, wherein the centers of the second light spots are located at different positions on the same track. 6. The optical disc apparatus according to claim 1, 2, 3, 4 or 5, wherein when recording information on the disc, one of the first and second optical spots is used. An optical disk device, wherein main recording is performed, and the other light spot assists the main recording.